Calender finished paper board product and process and means for production or treatment thereof



Dec. 31, 1948. g c (:QLBERT 2,226,709

CALENDER FINISHED PAPER BOARI) PRODUCT AND PROCESS AND MEANS FOR IPRODUCTION OR TREATMENT THEREOF Filed Feb. 9, 1939 INVENTOR.

/zar Zea C /Vja-odf avian/Z ATTORNEY.

Patented Dec. 31, 1940 uurrso STATES CALENDER FINISHED PAPER BOARD PROD-UCT AND PROCESS AND MEANS FOR PRO:- DUCTION OR IREATMENT THEREOF'Charles 0. Colbert, Elkhart, Ind., assignor to v American CoatingMills, Inc., Elkhart, Ind., a

corporation of Indiana Application February 9, 1939, Serial No. 255,468

20 Claims.

This invention relates to calender finished products comprising coatedand uncoated paper board, and to processes and means for use inproduction or treatment ofsuch finished products.

The paper board in a calender finished product is formed or providedwith a top liner or facing ply of relatively good paper; the remainingportion of the board, or the intermediate plies thereof, being composedof relatively inferior paper material, which may be produced from oldnewspaper stock 'or other coarse cheap pulp. The smoothly finished frontsurface of the product may be that of the paper liner, or of the paperliner treated or lightly coated with material to promote glossiness ofthe finish, or of a distinct film of coating material applied to thepaper liner. Calender finished paper board, in the sense of thisspecification, therefore includes ordinary calendered paper board;similar products formed with a facing ply of comparatively fine stockand highly finished by extended calendering; the so-called patent coatedpaper board which is finished with a glaze-like surface by extendedcalendering and treatment during calendering with a fine spray of thincoating solution, or by calendering, treatment and super calendering;and coated board produced by coating the face of ordinary calenderedpaper board with a paper coating solution, drying the coated board, andfinishing the dried coated board by supercalendering, usually with aglossy or lustrous finish. In the production of coated paper board ofthe, type last mentioned, the coating solution commonly employed is acomposition containing clay or the like, which when dried and finishedby supercalendering forms an enamel-like surface. Such coated paperboard, herein referred to as clay coated, is used extensively for themanufacture of merchandising cartons the labels of which are printed onthe fine printing surface provided by the film of coating material.

, Paper board, especially in thick and mediumthick grades, issubstantially reduced in thickness by calendering. A product subjectedto severe calendering to impart a high surface finish will be renderedthinner than one of the same weight or containing the same amount ofstock per square yard which is finished with only moderate calendering.Difierently finished products in coated. and uncoated paper board maytherefore have different weights in sheets of the same size andthickness, so that more stock may be required to obtain a specifiedthickness in one product than in another. Such products as patent coatedand finished clay coated paper board are generally relatively heavierthan ordinary calendered paper board of the same thickness. Finishedclay coated paper board, on account of the extra weight of its film ofcoating material, as well as on account of the degree ofsupercalendering which it undergoes in some instances, will ordinarilyoutweigh patent coated board of the same thickness. Though thediiferences in weights of the respective products may be slight orseemingly trivial, they will show up upon comparing substantial amountsof the respective products; since there will be more square feet ofboard in a ton of a relatively lighter product than in a ton of arelatively heavier product of the samethickness.

Both stiffness and lightness are desirable properties in paper board.The'lighter the product of a given thickness, the more of it can be madefrom a given amount of stock, and the more of it will be contained in aton furnished by the manufacturer to the customer.- A product relativelystiff for its thickness is usually to be preferred to thicker or heavierboard of the same stiffness or rigidity, other conditions being equal;

An object of the present invention is to obtain, in a calender finishedproduct comprising coated or uncoated paper board, an increment ofadditional thickness, or increased rigidity of the paper board, or both,without increasing the amount of stock in the paper board, and withoutdiminishing the degree of calendering for the production of suchfinished product. Further objects or advantages of the invention willhereinafter appear.

According to the invention, the calender finished paper board, coated oruncoated, after it has undergone the calendering for the finishing ofits front surface, is treated to impart additional rigidity or thicknessor both to the paper board, or to obtain in connection therewith one ormore of the other advantages hereinafter mentioned, by wetting ordampening the paper board by application of or introduction of moistureto or through the back of the board. In carrying out the invention, theboard may be treated as it is withdrawn from the calendering machine bywhich it is finished, or, if the finished product has been reeled orgathered in a roll, it may be treated as it is withdrawn from the reelor roll. Water or other suitable liquid 7 (which may be a treatingsolution to impart a desired property to the paper board) may be'applied substantially uniformly to the back of the board by wet rollsor by spraying or other suitable means, with appropriate regulation ofthe amount of water or liquid going into the paper board, which shouldbe sufiicient to render the 5 coarse paper material in the boardsubstantially damp, or to cause substantial impregnation of saidmaterial with the applied liquid by absorption thereof in said material.The preferred mode of dampening is by contacting the back 10 of theboard successively with a series of metalsurfaced rolls bearing films ofwater or treating liquid, the amount of water or liquid introduced intothe paper board being controlled by the number of wet rolls. A morerefined control 15 may be obtained, if necessary or desirable, by

associating with each of the wet rolls an adjustable squeeze rollcoacting therewith to regulate the thickness of the film of liquidcarried by such roll into contact with the paper board. In treatingfinished coated paper board having a clay coating, which coating andfinish thereof would not be impaired or objectionably affected bytemporary wetting, the board may be rendered substantially damp or evenquite wet throughout; 25 while in the case of a product whose frontsurface or' finish thereof would be impaired or objectionably affectedby moisture, the dampening operation may be controlled to avoidpenetration of moisture to such finished surface, or to 30 avoidsubstantial moistening of the top liner of the paper board or absorptiontherein of sufficient moisture to impair the smooth finish of its frontsurface. In this connection, attention may be called to the fact thatthe plies of the paper board composed of coarse paper material willquickly absorb moisture, whereas the top liner, being formed from morefinely beaten stock and of closer formation or texture, will be lessquickly moisture absorbent; so that it is practicable to regulate thewetting operation to cause substantial dampening of the coarse paperplies in the paper board without material or objectionable moistening ofthe top liner.

After the wetting or dampening operation, the dampened paper board issuitably dried by rapid dryingor partially by rapid drying. Rapid dryingmay be accomplished by blowing air across the back of the paper board,but preferably by first exposing the back of the paper board to a blastof hot air or to contact with heated air and then blowing air inopposite directions or alternately in opposite directions against andacross the back of the board. It is not intended to imply that the boardis completely dried, for it is desirable to retain a small amount ofmoisture in the paper board. In general the paper board will be dried toan appropriate degree of dryness for gathering the board in a roll or inpiles of cut sheets. During the drying, the paper board is drawn out andmaintained as taut as practicable, to resist tendency to buckle.

By the dampening of the paper board and ensuing drying, a desirableincrease in rigidity is 65 imparted to the paper board, which may beattributed to the swelling of the fibres in the coarse paper material.The material being in a compressed state, the swelling of the fibres byaction of moisture will cause them to pack still 70 more closelytogether, with resultant rigidifying effect in the dried product. Soalso the swelling of the fibres as they absorb moisture will tend toswell the paper board as a whole. Assumin sufiicient absorption ofmoisture in the paper 75 board to cause appreciable swelling of thepaper board from less stock per square yard than has board, the productafter drying will be fiufller or lighter for its thickness than when itwas delivered from the calender finishing operation, and therefore offlufiier or lighter quality than similarly finished paper board of thesame thick- 5 ness as conventionally produced by operations concluded bythe calender finishing. By the effect of the dampening operation, asubstantial increase in the thickness of the calender finished paperboard may be obtained, especially in thick and medium-thick grades ofpaper board. In the case of supercalendered clay coated paper board of16 points thickness as delivered from the supercalendering rolls, I havefound it practicable to obtain, as an efiect'of swelling of the board bymoisture, an increase in thickness up to points by gauge measurement.

From the foregoing it will be seen that the invention offers opportunityof obtaining rela tively stiffer and lighter products in calenderfinished paper board having an unimpaired fine printing surface, and ofproduction of such products as patent coated and finished clay coatedpaper board in' sheets comparing favor-. ably as to lightness of weightwith one another and with ordinary calendered paper board of the samethickness. In general the invention offers opportunity for manufactureof calender finished products comprising coated and uncoated paperformerly been required, with resultant economy in large scaleproduction.

Attention is invited to another important aspeot of this invention inconnection with the manufacture of coated paper board by coating thepaper board with a coating solution, drying the coated paper board whileit hangs in festoons or folds from supporting poles, andsupercalendering the dried coated board. As an efiect of hanging thecoated paper board from the sup- 40 porting poles, there are producedwhat are known as pole marks, which in'the finished product are neitherdiscolorations nor deformations but are visible effects somewhatsuggestive of water marks. There are also produced what are known ascheck marks" appearing at the back of the board, these being suggestiveof minor disturbances in the coarse paper material. An advantage of thepresent invention is that the dampening or wetting of the paper boardtends to promote removal or substantial diminution of such pole marksand check marks. For this object it is desirable to render the paperboard quite wet, which is practicable in the case of 5 clay coated paperboard without objectionably affecting the smoothness of the finishedsurface of its coating.

The invention further offers opportunity in connection with themanufacture of calender 0 finished coated and uncoated paper board topractice auxiliary processes whereby to impart a desired property orcharacteristic to the paper board. Thus it is contemplated that thedampening of the board as hereinbefore described may be accomplishedwith the use of an aqueous or other suitable treating solution to imparta waterproofing or grease proofing quality or other property to thepaper board by substantial inipregnation with solution containingappropriate ingredients. Or in connection with the moistening of thepaper board by water there may be a supplemental treatment with greaseproofing, waterproofing or other liquid to impart a desired quality orcharacteristic to the paper material. It is also contemplated that theboard may be treated with a solution containing an ingredient to promotefiufl'iness.

Again, in the case of a calender finished product the back ply of whichis formed from the unattractive looking gray stock obtained from oldnewspapers, an improvement in the appearance of the back side of thepaper board may be obtained by taking advantage of the wet state of thecalenders I l the paper board sheet 10 as shown).

coarse paper material to imprint a design on the back side of the board,by carrying it over a suitable roller to imprint such design. Forexample the board while in the wet state may be drawn over a roller toimpart to the back side of the board an appearance simulating alligatorskin or the like.

Reference will now be made to one illustrative practice of the inventionin connection with the manufacture of coated paper board by a preferredmethod; it being understood that the illustrative practice is exemplaryand that the following description with references to the drawing, whichis diagrammatic, is not to be taken as limiting the invention beyond theterms of the claims.

In the accompanying drawing:

Fig. 1 is a diagram representing a plant for manufacture of coated paperboard and embodying means for practicing the present invention.

Fig. 2 is a diagrammatic representation of the portion of said plantwhich comprises the supercalendaring machine and apparatus for treatingthe finished coated board as it is drawn from the supercalenderingmachine.

The diagram in Fig. 1 represents a plant of the type disclosed in UnitedStates patents to Colbert et al. No. 1,514,439 of November 4, 1924 andNo. 1,903,325 of April 4, 1933, wherein paper board is continuouslyproduced from wet stock on a board making machine and subjected to thesuccessive operations for production of the finished coated productwithout reeling the board between successive stages of manufacture. Inthe drawing the numeral l0 designates the line of paper board comingfrom the board making machine and undergoing said successive operations.From the drying section of the board making machine (not shown) thepaper board runs through the for ironing out the board and smoothlyfinishing the surface provided by its top paper liner (such surfacebeing the top side of The calendered paper board may receive at l2 apreliminary thin coat of coating solution, as in Patent No. 1,903,325,and the board is then conveyed to a suitable hang-up apparatus in whichthe board is hung up in festoons or folds for drying. asindicated at I4;the hang-up apparatus permitting variable accumulation of hanging foldsin its de livery end. From the delivery end of the hang'-'-- surface acoating solution of similar composi-' tion and color to that previouslyapplied but somewhat thicker. The coating solution may be a compositioncontaining clay or the like (for example a composition of clay andcasein, with or without coloring pigments or aniline coloring matter,and which may contain suitable percentages of sizing and otheringredients commonly used in clay type coating solutions). The coatedpaper board is fed into the drying room IS in which the board hangs infestoons or folds for drying, the hang-up apparatus permitting variableaccumulation of hanging folds in the delivery end of the drying room.The dried coated board is drawn from the drying room past 1 aligning,tensioning and smoothing appliances I! to and throughthe-supercalendering machine l8, or through such portion of the stack ofsupercalendaring rolls as may be required for ironing out the board andimparting the desired finish to its clay coating.

As represented in the drawing, the finished coated board is drawn fromthe supercalendering machine over a guide roll I9 and then over a seriesof wet rolls 20 contacting with the under side or back of the board,whereby the paper board or coarse paper material thereof issubstantially dampened as hereinbefore described. A pan containing wateror treating solution in which the wet rolls are partially submerged isindicated at 2|. The wet rolls may be driven to rotate at a surfacespeed equal to the speed of travel of thepaper board, or at a slightlyless or greaterspeed for varying the amount of water carried by eachroll into contact with the paper board. Beyond the wet rolls the boardmay be engaged by coacting slitter disks 22 for trimming the edges ofthe board or cutting it longitudinally. There may be a pair of coactingdisks for trimming each side of the board, and one or more intermediatepairs of coacting disks for dividing the board longitudinally. Anadvantage in this connection is that the dampened board cuts easily,ofiering much less resistance to the slitting operation than in the caseof dry paper board. After the dampening of the board, it is subjected torapid drying action, which may be initiated by passing the board overthe open-topped hot air box or chamber 23 to which hot air is suppliedby the pipe 24. The back of the board is thus exposed to a blast of hotair, with consequent drying or partial drying efiect. It will be understood that as the back ply of paper board becomes dry it will drawmoisture from the next ply, so that the efiect of exposing the board tohot air will be to check further penetration of moisture in the board.Further rapid drying may be obtained by blowing air against the back ofthe board or back and forth in opposite directions across the back ofthe board. In the diagrammatic representation shown, two blowers areindicated at 25 and 26, the blower 25 being arranged to blow air underand across the board from one side, and the blower 26. being arranged toblow air under and across the board from the opposite side. There may beasmany blowers as may be r'equiredfor drying the paper board to anappropriate degree of dryness. Beyond the blowers the from thesupercalendering machine, and runs it appropriate speed to maintaintheboard drawn out in taut condition. The suction conveyor may be driven ataspeed slightly in excess of the speed of the paper board as it leavesthe calendering -machine, to take up slack and maintain the board taut.The driving mechanism for the suction conveyor may include a frictionclutch which will slip when the tension of the board exceeds apredetermined value. At 28 are indicated a pair of coacting cutter rollsfor cutting the board into sheets. The upper roll may have a cutterblade which at every revolution will register with a groove in the lowerroll. The out sheets may be taken off by conveyor means or may drop intothe tray 29. If desired the upper roll may be removed and the finishedboard may be gathered in a roll 30.

It will be understood that the details of the illustrative practice andapparatus may be variously modified to suit different requirements andconditions in the manufacture of calender finished coated and uncoatedpaper board of various specific types. In carrying out the invention, itis desirable to dampen the paper board by introducing from about 45% to55% of its weight of moisture, whereby to obtain appreciable swelling ofthe paper board by moistening action, while avoiding such excess ofmoisture in the board as to require correspondingly increased dryingcapacity. However the invention is not intended to be restricted to theuse of the proportion of moisture stated nor to any proportions.

I claim as my'invention:

1. In the production of a calender finished product comprising coated oruncoated paper board having a smoothly finished facing ply, the processwhich comprises finishing the board by calendering, dampening thefinished board by application of liquid to the back of the board afterit has undergone its final calendering, and drying the dampened board.

2. In the production of a calender finished product comprising coated oruncoated paper board having a smoothly finished facing ply, the processwhich comprises finishing the board by calendering, and, after it hasundergone its final calendering, introducing through the back of theboard sufficient moisture to render the coarse paper material in theboard substantially damp, and drying the dampened board.

3. The process of treating calender finished paper board having asmoothly finished facing ply which comprises dampening the finishedpaper board by application of liquid to the back side of the board afterit has undergone its final calendering, and drying the dampened board.

4. The process of treating calender finished paper board having asmoothly finished facing ply which comprises introducing through theback side of the board sufficient moisture to cause appreciable swellingof the paper board and drying the moistened board, said treatment beingafter the board has undergone its final calendering.

5. The process of treating calender finished paper board having asmoothly finished facing ply which comprises dampening the coarse papermaterial of the finished board by application of moisture to the back ofthe board after it has undergone its final calendering, while avoidingsubstantial moistening of the finished front surface of the board, anddrying the dampened board.

6. The process of treating calenderfinished paper board havinga'smoothly finished facing ply which comprises causing appreciableswelling of the finished board by action of moisture, the moisture beingintroduced through the back side of the board after it has undergone itsfinal calendering, and drying the board by rapid drying actioncommencing after appreciable swelling and before absorption by saidfacing ply of suffipaper board sufilciently to cause appreciableswelling of the board, by introduction of moisture through the back ofthe board, and rapidly drying the board while drawing it taut, saidtreatment being after the board has undergone its final calendering.

9. In the process of making coated paper board 4 by coating calenderedpaper board with coating solution, drying the coated board while hangingit in festoons or folds, and supercalendering the dried coated board,the improvement which comprises dampening the paper board aftersupercalendering by application of moisture to the back of the board,and drying the dampened board.

10. The process of treating calender finished paper board having asmoothly finished facing ply which comprises impregnating the finishedpaper board with liquid to impart a desired property to the paper board,the impregnating liquid being introduced by application to the back sideof the board, said treatment being after the board has undergone itsfinal calendaring.

11. The process of treating calender finished paper board having asmoothly finished facing ply which comprises wetting the back portion ofthe finished board and drawing it while wet over a roll having a surfaceformed for imparting a design to the back side of the board; saidtreatment being after the board has undergone its final calendering.

12. In apparatus for treating paper board, the combination with acalendering machine of moistening and drying apparatus beyond said cal-,endering machine and through w'hich the board is drawn from thecalendering machine, said moistening apparatus comprising means fordampening the paper board by application of 50 liquid to its bottomside.

13. In apparatus for treating paper board, the combination with asupercalendering machine, of a series of wet rolls contacting with thebottom side of the board as it is drawn from the calendering machine.

14. In apparatus for treating paper board, the combination with acalendaring machine, of a suction conveyor beyond and remote from thecalendaring machine, by which the board is drawn taut, means fordampening the board delivered from the calendering machine byapplication of liquid to its back side, meansfor longitudinally slittingthe board while damp, means for drying the dampened board, saiddampening, slitting and drying means being in advance of the suctionconveyor, and means beyond the suction conveyor for cutting the boardtransversely.

15. Calender finished paper board having a surface satisfactory forprinting and characterized by a higher degree of fiufiiness and rigiditythan when delivered from'the calendering operation by which it wasfinished.

16. Clay coated paper board finished by supercalendering, having asurface satisfactory for 7 printing and characterized by a higher degreeof fiumness and rigidity than when delivered from the supercalenderingoperation.

17. The process of treating calender finished paper board having asmoothly finished facing ply, to obtain flufiing and rigidifyingeffects, which comprises dampening the finished paper board suflicientlyto cause appreciable swelling thereof by application of liquid to theback side of the board after it has undergone its final calendering,while avoiding sufficient absorption of moisture by said facingply tomaterially impair the smooth finish of its surface, and drying thedampened board. v

18. The treatment of suprcalender-finished clay coated paper board, toobtain fiufling and rigidifying effects, which comprises introducingthrough the back side oi the board sufiicient moisture to causeappreciable swelling thereof and drying the moistened board, saidtreatment being after the board has undergone its final calendering.

19. The treatment of supercalender-finished clay coated paper boardwhich comprises dampening the paper board substantially throughout thethickness of its coarse stock portion by application of liquid to theback side of the board after it has undergone its final calendering, anddrying the dampened board.

' 20. The treatment of supercalender finished coated paper board havinga front surface of coating material smoothly finished by thesupercalendering which comprises dampening the paper board byapplication of liquid to its back side after the supercalendering, whileavoiding mois-

